Pulse-width dependence of laser damage in optical materials: critical analysis of available data and recent results for nanopicosecond region

摘要

A critical analysis of available theoretical and experimental data for a pulse-width dependence of laser induced damage thresholds (LIDT) in various optical materials is given along with new results of our recent measurements obtained in nano-picosecond range at 1064 nm wavelength for alkali halide crystals (NaCL, KCl, KBr). Three YAG:Nd laser oscillator-amplifier systems operating in Q-switch and mode-locking modes provided highly stable light pulses at 2 ns, 15 ns, and 50 ps with Gaussian spatial profile of beams were used in the experiments. Special attention was paid to the comparability of the LIDT test conditions for various pulse widths, implying the carefully controlled similarity of beam intensity spatial distributions and temporal profiles. The experimental data are analyzed on the basis of theoretical predictions for different damage mechanisms. It is concluded that pulse-width scaling of LIDT is still a problem, and an adequate approach to its solution is formulated.